Opinio Juris: Between Mental States and Institutional Objects

This chapter addresses the role of international organisations in the formation of Customary International Law from a specific viewpoint: whether international organisations, which knowingly have many instruments to shape the behaviour of States, are also capable of shaping the opinio juris of States. For instance, would an international organisation such as the United Nations be able to promote, or at least influence the formation of opinio juris that is consistent with findings and recommendations of the Intergovernmental Panel on Climate Change? To develop my argument, I organise the chapter in two main parts – a study into the concept of opinio juris, and a study into the ability of international organisations to promote opinio juris with a desired content. This work concludes by playing down the possibility that international organisations are able to coordinate international processes in a manner to shape opinio juris pursuant to desired standards.